Charging in wireless networks has traditionally been either postpaid or prepaid. Postpaid charging refers to the type of charging in which a subscriber uses a service prior to paying for the service. For example, a subscriber may enter into a contract with a service provider specifying what the subscriber will be billed for the service. As the subscriber places or receives calls over the network, an administrator server or the like collects call information during each call and generates a call detail record for the call. The call detail record includes information such as the calling party, the called party, the duration of call, etc. The call detail records are collected by a billing system of the service provider that aggregates the call detail records for a billing cycle. At the end of the billing cycle, the service provider sends out a bill to the subscriber that specifies the usage by the subscriber during the billing cycle.
Prepaid charging refers to the type of charging in which a subscriber purchases the service prior to use and the balance paid for by the subscriber is depleted based on the usage by the subscriber. For example, a subscriber may purchase five hundred hours of airtime in a prepaid wireless plan. As the subscriber places or receives calls over the wireless network, an administrative server or the like in the network monitors the usage by the subscriber in real-time and decrements the account of the subscriber accordingly. If the subscriber's account runs low or runs out, then the subscriber needs to recharge the account before further usage will be granted by the network.
As the prepaid airtime subscriber uses a mobile terminal during active mode (when a voice or data call is established or when SMS or MMS messages are sent or received), the balance of remaining available airtime diminishes from the initial prepaid subscription. Unless the user has kept track of the minutes used, and knows the tariff or roaming charges, the user must rely on the service provider to inform him of the remaining balance. To learn the remaining balance of a prepaid subscription, a balance query is initiated by the user while the mobile terminal is not in the active mode or the mobile service provider sends text or voice messages to the mobile terminal with the balance information whenever an event affecting the balance occurs.
However, while the mobile terminal user desires to know the exact and detailed remaining balance to manage his or her mobile service account, such a user-initiated notification or service provider's notification by text or voice messages often cannot reflect the exact remaining balance in real time. The user-initiated balance notification cannot provide the mobile station with the real time balance when the user does not request information of the remaining balance after every balance affecting event occurs. In addition, a service provider's notification cannot provide real time balance to the mobile station when the mobile station is powered off or moves out of the coverage area for some period.
As a way to provide the real time balance to the mobile terminal user, some platforms send Short Message Service (SMS) messages including the remaining balance and/or expiration date to the mobile terminal for display, whenever an event affecting the balance occurs. When the mobile terminal receives such an SMS message, the balance is updated and displayed on a display of the mobile terminal as to permit the user to know the balance and the expiration date in real time. This notification scheme based on the SMS messages works well as long as the mobile terminal is powered on and ready to receive the SMS messages at the appropriate time. However, if the balance affecting event occurs while the mobile terminal is powered off, if the mobile terminal is not in the coverage area, or if the mobile terminal remains powered off or out of range longer than the period for which the network retains the SMS message before the messages are discarded, then the remaining balance displayed on the mobile terminal does not accord with the remaining balance stored in the network.
Hence, a need exists for a technique for synchronizing prepaid account balance of the mobile station with the prepaid account balance stored in the prepaid server.